On the role of the coriolis and quasiparticle-phonon interactions in describingE1 transition probabilities in odd Eu and Tb isotopes

Study of the nuclear second moments, important inputs to pre-equilibrium reaction theories, is extended to residual interactions of finite range. The interactions are assumed to have general spin and isospin dependence. The second moments are found to be always positive definite for commonly used values of the interaction parameters. They seem to support the strong coupling limit of the pre-equilibrium reaction theory by Nishioka et al. [1], which would imply the modification of the phenomenological model used in analyzing experimental data. As an application of the second moments, it is also investigated how the nuclear level densities change with the parameter values of the residual interaction. The results show the important role of the residual interaction especially in the low energy region, which may greatly improve the agreement with experimental data at thermal neutron resonances.     

Precision measurements of nuclear quadrupole moments by muonic X-rays

The electric multipole hyperfine interaction in muonic atoms is discussed. In particular, the influence of the finite size of the nuclear electric multipole-charge distribution on the values of nuclear spectroscopic multipole moments that are extracted from muonic hyperfine measurements is considered. It is shown that nuclear electric quadrupole moments can be deduced from the observed hyperfine splittings of muonic M X-ray transitions with high precision and practically independently of the model nuclear quadrupole-charge density. Measurements of the ground-state electric quadrupole moments of 11 deformed nuclei in and near the rare-earth region are discussed.     

Nuclear charge radii,nuclear moments,and nuclear structure

New and systematic measurements of nuclear charge radii and nuclear moments are providing a deeper insight into properties of nuclei. In this article, the implications of these new measurements on our understanding of collective properties of nuclei are discussed.     

Chemisorption of Li and Na on iridium surfaces: An investigation with nuclear spin polarized atoms

The chemisorption of Li and Na on clean and oxygen covered polycrystalline iridium was investigated using nuclear spin polarized alkali atoms. During adsorption on the surface the moments of the nuclei act as microscopic probes. The nuclear quadrupole moments of the alkali atoms are interacting with the electric field gradient. The interaction reflects the charge distribution around the nucleus. The nuclear magnetic moments are interacting with magnetic fields generated by the magnetic moments of electrons.     

Integral representations for Schwinger functionals and the moment problem over nuclear spaces

It is shown that a continuous positive linear functional on a commutative nuclear *-algebra has an integral decomposition into characters if and only if the functional is strongly positive, i.e. positive on all positive polynomials. When applied to the symmetric tensor algebra over a nuclear test function space this gives a necessary and sufficient condition for the Schwinger functions of Euclidean quantum field theory to be the moments of a continuous cylinder measure on the dual space. Another application is to the problem of decomposing a Wightman functional into states having the cluster property.     

The understanding of nuclear structure through Mössbauer experiments

Mössbauer's discovery vitalized the study of hyperfine interactions on nuclear states. The technique has been used to measure the electromagnetic moments of scores of nuclear levels and the results, especially on rotational states, have been important to our understanding of nuclear structure. Equally signicant for nuclear physics has been the deep insight which Mössbauer studies have given us of the hyperfine interaction itself; using that knowledge, and a variety of techniques, the measurements of nuclear magnetic moments are now reliable and routine.     

Can we see relativistic and quark effects in nuclear magnetic moments?

Many theoretical contributions to nuclear magnetic moments are reviewed with major attention to core polarisation and meson exchange currents. Experimental evidence is drawn from light isobaric mirror nuclei. Relativistic and quark contributions to nuclear magnetic moments are estimated and discussed.     

Toward a theory of nuclear relaxation in dielectric glasses at ultralow temperatures

The temperature and frequency dependence of the nuclear relaxation rate in dielectric glasses is investigated. It is shown that at low and ultralow temperatures nuclear relaxation is due to an interaction between the nuclear quadrupole moment and fluctuations of the electric field created by dipole moments of two-level systems. Fluctuations of this field can be associated with the background relaxation or are due only to the dipole-dipole interaction between two-level systems. It is shown that at lower temperatures the second relaxation mechanism begins to dominate. Expressions are obtained for the temperature and frequency of crossover between different nuclear relaxation regimes. The possibility of experimental confirmation of our results is discussed. Zh. éksp. Teor. Fiz. 115, 2254–2262 (June 1999) Russian Scientific Center “Kurchatov Institute”     

Isoscalar currents and nuclear magnetic moments

We investigate meson-exchange current effects on isoscalar nuclear magnetic moments taking a one-boson exchange model. For some cases we find appreciable contributions, though the results are very model dependent. We also discuss the connection between exchange currents and the calculation of magnetic moments in the relativistic σ-ω model.     

Effective hamiltonian of the nuclear moments electronic shielding

An information is given allowing to use the second quantization and the effective operator methods in the ligand field theory. The operator was constructed accounting for the interaction of the multi-shell electronic configurations through a one-particle perturbation V≪R. The expression obtained is believed to be useful in microscopic calculations and phenomenological interpretation of spectroscopic experiments. As an illustration, the effective hamiltonian of the nuclear moments electronic shielding has been deduced. It was found, in particular, that the dipolar part of the hyperfine interaction contributes to the shift of the nuclear g-factor in the systems with the electronic spin S>0.     

On the deviation of small nuclear systems from saturation

Below a definite thickness, the structure of nuclear slabs — treated in the energy density formalism — deviates from saturation, and in particular the surface tension decreases rapidly. These effects, seemingly a consequence of the finite range of nuclear forces, cannot be accounted for by the droplet-model concept. A (negative) correction term is proposed for the nuclear mass formula which becomes important for small nuclei in addition to the (positive) curvature energy. Its consideration may remove ambiguities in theoretical predictions and empirical values of the curvature energy.     

Revision of spin echoes in pure nuclear quadrupole resonance

Goldman's spin-1/2 formalism has been used for describing the response of an I=3/2 spin system to a two-pulse sequence in a pure nuclear quadrupole resonance experiment. A detailed analysis of the polarization evolution and quadrupolar echo generation is carried out through the use of explicit expressions for secular homo- and heteronuclear dipolar interactions. In striking contrast with previous studies, it is predicted that Van Vleck's second moments governing a classical solid-echo or Hahn sequence differ from those obtained by equivalent means in magnetic resonance. In fact, it is shown that, although measured moments still complement each other, the combined use of standard sequences does not allow the separate determination of homo- and heteronuclear dipolar contributions to the linewidth, not even in an indirect manner. In this context, the importance and potential usefulness of a crossed coil probe are also briefly discussed.     

From the NN interaction to nuclear structure and reactions

We present a novel approach for the treatment of realistic nucleon-nucleon interactions in nuclear many-body systems. A unitary correlation operator is used to explicitly introduce short-range central and tensor correlations in many-body states. The correlated interaction is used as an effective interaction in nuclear structure calculations. Results for Lithium isotopes including proton and neutron distributions, radii as well as magnetic moments and quadrupole moments are shown. Molecular resonances in the ¹⁶O?¹⁶O system are given as a first application in reaction theory.     

Line shape analysis in nuclear quadrupole resonance spectroscopy (I=3/2)

Following the treatment of Vega (1973), the theoretical expressions for the second moments in nuclear quadrupole resonance (nqr) due to dipole-dipole interactions have been derived for the system containing the nuclei with spinI=3/2. Cases with the orientation of the static magnetic field and the interactions with the other magnetic nuclei are also dealt with.     

Nuclear moments. Concluding remarks

Studies of nuclear magnetic moments and nuclear weak interactions discussed in this Conference are reviewed. The importance of configuration mixing and meson exchange currents is examined, and it is emphasized that the second order configuration mixing (tensor correlation) is essential for the understanding of these phenomena. Recent results concerning nuclear quadrupole moments reported in this Conference are also discussed. Finally, the pairing effect in metal clusters is pointed out and the importance of measuring their spins and magnetic moments is mentioned.     

Nuclear moments: An effective probe of nuclear stucture

Magnetic dipole and electric quadrupole moments are discussed in nuclei near doubly-closed shell nuclei (the T1 nuclei) and in nuclei along series of single-closed shell nuclei (plus of minus a few nucleons) (the In odd-mass and odd-odd nuclei). We discuss the “additivity” rules for nuclear moments. We also address the EO moment: the liquid drop model and the shell-model are discussed and compared to measurements of nuclear radii in the Ca, Sn and Pb region. In the latter region, the importance of intruder states across the Z=82 proton closed shell is emphasized.